Process for deodorizing exhaust gas containing smelly components

Abstract

A process for deodorizing an exhaust gas containing at least one smelly material selected from the group consisting of acidic smelly materials, such as hydrogen sulfide, mecaptans, dimethyl sulfide, dimethyl disulfide and the like; basic smelly materials, such as ammonia, amines and the like; and smelly organic material, such as ketones, alcohols, aldehydes, carboxylic acids and the like is disclosed. Vapor-liquid contact of the exhaust gas with a sodium hypochlorite solution is caused in the presence of a catalyst which is a mixture of nickel peroxide and at least one carrier. In the presence of the catalyst, placed in a column, sodium hypochlorite solution falling from the upper portion of the column contacts exhaust gas rising from the lower portion of the column to promote catalyst oxidation reaction. The amount of sodium hypochlorite solution fed into the upper portion of column is adjusted so that the concentration of the sodium hypochlorite solution in the bottom of column is maintained at such a desired value that optimum oxidation reaction occurs, and sodium hydroxide solution is added to the sodium hypochlorite solution so that pH of the sodium hypochlorite solution in the bottom of the column is kept within the range of from 7.5 to 11.0.

We claim: 
     
       1. A process for deodorizing an exhaust gas containing at least one smelly material selected from the group consisting of acidic smelly materials, basic smelly materials, and smelly organic materials, and including at least hydrogen sulfide and ammonia, comprising: causing vapor-liquid contact of the exhaust gas with a sodium hypochlorite solution in the presence of a catalyst, said catalyst being a mixture of nickel peroxide and at least one carrier,   wherein said causing step comprises contacting, in a column having an upper portion and a lower portion with said catalyst placed therein, sodium hypochlorite solution falling from the upper portion of the column with exhaust gas rising from the lower portion of the column to promote catalytic oxidation reaction, the amount of sodium hypochlorite solution fed into the upper portion of the column being adjusted so that the concentration of the sodium hypochlorite solution in the bottom of column is maintained at such value that optimum oxidation reaction occurs, and   wherein a sodium hydroxide solution is added to the sodium hypochlorite solution so that the pH of the sodium hypochlorite solution in the bottom of the column is kept with the range of from 7.5 to 11.0.   
     
     
       2. The process as defined in claim 1 wherein the sodium hydroxide solution is added to the sodium hypochlorite solution so that pH of the sodium hypochlorite solution in the bottom of the column is kept within the range of from 8.5 to 9.5. 
     
     
       3. The process as defined in claim 1 wherein a bed of filler not containing nickel peroxide is further charged over the bed of catalyst in said column. 
     
     
       4. The process as defined in claim 1 wherein the solution of sodium hypochlorite is circulated from the bottom of said column to the top of said column, and a fresh solution of sodium hypochlorite and a solution of sodium hydroxide are added to the circulating solution of sodium hypochlorite. 
     
     
       5. The process as defined in claim 1 wherein before the exhaust gas is introduced into the oxidizing column, the gas is washed in a washing column with the solution of sodium hypochlorite discharged from the oxidizing column. 
     
     
       6. The process as defined in claim 1 wherein the exhaust gas discharged from the oxidizing column contacts activated carbon, zeolite or a mixture of activated carbon and zeolite to remove oxidizing materials from the gas. 
     
     
       7. The process as defined in claim 1 wherein the catalyst is prepared by blending a chlorine and/or fluorine-containing resin and nickel peroxide, molding the blending and curing it. 
     
     
       8. The process as defined in claim 7 wherein at least one inorganic material powder selected from the group consisting of synthetic zeolite, ceramic, and alumina is further blended with the chlorine and/or fluorine-containing resin and nickel peroxide. 
     
     
       9. The process as defined in claim 1 wherein the catalyst is prepared by blending a chlorine and/or fluorine-containing resin and at least one nickel compound selected from the group consisting of nickel sulfate, nickel nitrate, nickel carbonate and nickel hydroxide, and molding the blending and curing it, and then contacting the molding with an alkali metal hydroxide and an oxidizing agent to convert the nickel compound to nickel peroxide. 
     
     
       10. The process as defined in claim 9 wherein at least one inorganic material powder selected from the group consisting of synthetic zeolite, ceramic, and alumina is further blended with the chlorine and/or fluorine-containing resin and the nickel compound. 
     
     
       11. The process as defined in claim 1 wherein the catalyst is prepared by having a carrier selected from the group consisting of chemical-resistant resin moldings and inorganic material moldings, bear nickel peroxide with the use of a chlorine and/or fluorine-containing resin solution as an adhesion medium; or having said carrier bear a mixture of nickel peroxide and the chlorine and/or fluorine resin solution. 
     
     
       12. The process as defined in claim 1 wherein the catalyst is prepared by having a non-treated carrier selected from the group consisting of chemical-resistant resin moldings and inorganic material moldings, bear at least one nickel compound selected from the group consisting of nickel sulfate, nickel nitrate, nickel carbonate and nickel hydroxide with the use of a chlorine and/or fluorine-containing resin solution as an adhesion medium, and then contacting the carrier with an alkali metal hydroxide and an oxidizing agent to convert the nickel compound to nickel peroxide; or having the non-treated carrier bear a mixture of said nickel compound and said chlorine and/or fluorine resin, and then contacting the carrier with an alkali metal hydroxide and an oxidizing agent to convert the nickel compound to nickel peroxide. 
     
     
       13. The process as defined in any one of claims 11 and 12, wherein said carrier molding is of a material selected from the group consisting of polyvinyl chloride resin, polyethylene resin, polypropylene resin, fluorine resin, synthetic zeolite, ceramic and alumina.